Group III nitride, for example, a gallium nitride (GaN) based semiconductor is expected to be used as a material for next-generation power semiconductor devices. The GaN based semiconductor device has a wider bandgap than that of a silicon (Si) semiconductor device, and thus can achieve a high breakdown voltage and a low loss in comparison to the Si semiconductor device.
A High Electron Mobility Transistor (HEMT) structure using a two dimensional electron gas (2DEG) as the carrier is widely applied to a GaN based transistor. A junction HEMT is one type of GaN based HEMTs.
For example, using a p-type GaN based semiconductor for a gate electrode in a junction HEMT can achieve the normally off operation. Meanwhile, injecting a positive hole (hole) from the gate electrode to a channel causes conductivity modulation. This can reduce the on-resistance of the junction HEMT. However, the injection of a hole unfortunately increases the switching time of the junction HEMT.